Oral communication is a vital element in education, employment, social functioningand self- expression. At least 89% of the one and one half million individuals diagnosed with idiopathic Parkinson's disease (IPD) have a speech or voice disorder, yet only 3-4 % receive speech treatment. Generation of the first voice treatment efficacy data has provided important information about mechanisms underlying the voice disorder in IPD and has identified fundamental elements of treatment-related change. The work proposed here builds upon this well-established foundation of data to accomplish the following aims: (1) evaluate the system- wide generalized impact of voice and articulation treatments on speech articulation, facial expression and swallowing; (2) evaluate the system-wide generalized impact of voice and articulation on treatments on limb gesture and limb motor functioning; (3) investigate laryngeal sensorimotor gating and internal cueing in IPD and the impact of voice and articulation treatments on such deficits; (4) investigate the effects of voice treatment on brain functional activity using Position Emission Tomography (PET). These studies will simultaneously advance knowledge of basic mechanisms underlying disordered voice and effective treatment, while directly contributing to improved communication and quality of life in individuals with neurological disorders.